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The most obvious way that humans use natural selection is in breeding animals. You've probably heard of Chuweenies (a cross between a chihuahua and a Dacshund or weiener dog); or labradoodles (a cross between a Labrador and poodle). Even less exotic breeds like St. Bernards and German Shepherds have all been bred to have certain characteristics that are beneficial to humans. Artificial selection helped to achieve the desired characteristics.
Plants also have been bred to have different characteristics. Cross-breeding of pea plants by Gregor Mendel revealed how genetic heredity works. Today we cross-breed plants that are resistant to drought or pesticides with crop plants to grow hardier plants for food. Plants that can survive droughts, be sprayed against weeds, don't need to be sprayed as much against insects.
You ever watch a horse race? Did you notice that they frequently have the breed age, and lineage of the horse? This is because racers have noticed that many of the qualities that make a good racehorse are hereditary. Breeding of the horse can make a better racehorse, and benefit others. And just like dogs, different horses are better for different tasks, so they get bred to have more of the traits that will make a better workhorse, a better racehorse, a better jumper.
There are some drawbacks always. Some of the plants that have natural pesticides may be contributing to Colony Collapse Disorder in Honeybees. Racehorses don't have much of a future once they are past their racing years. Greyhounds were bred to be fast runners, but as the sport lost popularity, few uses were found for greyhounds, as their traits lost value.
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